Transformer



Dec. 29, 193.1. c, w KRONMlLLER 1,839,038

TRANSFORMER Filed July 22, 1931 Invefltav: Charles W. Kronmiem His Attorwe'aq.

Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE CHARLES W. KRONIILLER, F FORT WAYNE, INDIANA, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK TRANSFORMER Application filed July 22, 1931. Serial No. 552,436.

My invention relates to transformers. Some transformers are used to supply cur rent to secondary or loadcircuits of such character as to cause very high frequency oscillations to appear in the currents flowing in the secondary circuits which include the secondary windings of the transformers. These oscillations send out corresponding high frequency waves ofenergy which, if m allowed to spread, will interfere seriously with radio reception. Many oil burner ignition circuits used in heating systems for residences and other buildings are of this character, the fuel oil being ignited by an are or spark which is maintained by current from a transformer. Several thousand volts from the transformer secondary are usually necessary to maintain such an arc and the primary of the transformer is usually connected to any convenient low voltage source of current such as a lighting or power circuit. A direct spread of high frequency energy from the transformer and its secondary circuit may be-easily prevented by suitable metallic casings and conduit but there has been difliculty in preventing the high frequency oscillations in the secondary circuit from being transmitted back through the transformer into the lighting or power system or other source of primary current whence the energy may spread and interfere seriously with radio reception. Radio interference is also materially reduced by arranging the trans former windings and their connections symmetrically and by making the secondary connections short and symmetrically spaced from any ground connections. The general object of the invention is to provide an improved transformer construction including a conductive shield arranged to reduce still further the interference with radio reception.

The invention will be better understood from the following description taken in con- 45 nection with the accompanying drawings in two series-connected sections 16 and 17 surwhich Fig. 1 shows a transformer construct ed with a conductive shield in accordance with the invention; Fig. 2 shows the conductivecshield; andFig. 3 is a diagrammatic view of the transformer and its connections.

Like reference characters indicate similar parts in the different figures of the drawings.

The invention will be explained in connection with the transformer shown in Fig. 1 of the drawings. This transformer includes a magnetic core 10 having two winding legs 11 and 12 connected by yokes 13 and 14. A primary winding 15 surrounds the winding leg 11 and a secondary winding formed in rounds the winding leg 12. These sections 16 and 17 of the secondary windin are spaced slightly apart and arranged side by side and symmetrically with respect to the center of their winding leg 12. A magnetic shunt 18 extends bet-ween the two core yokes 13 and 14 with a short air gap at each end. This magnetic shunt with its air gaps forms a high reluctance by-pass for the main core flux and thus limits the amount of secondary current which can flow in the secondary winding and the circuit connected to it in case this secondary circuit is accidentally short circuited. The presence of this high reluctance shunt also permits the secondary winding to have a very high voltage on open circuit so as to start an arc in the circuit and then to cause this voltage to drop -to a suit able lower value-to'maintain the arc.

A shield 19 of conductive material such as brass or copper surrounds the winding leg 12 in the space between the two sections 16 and 17 of the secondary winding. .This shield 19 is a flat conductive member with a central opening for the winding leg 12 and a ga 20 at one side so that it does not form a s ort circuited turn around the winding leg.

The two sections 16 and 17 of the secondary winding are connected in series by connecting their inner terminals 21 and 22 rean Transformers with symmetrically arranged v windings, a magnetic shunt between the primary and secondary windings and a double section secondary winding with its center grounded have been previously proposed and used andhave been found effective in preventing excessive radio interference due to core, primary and secondary windings on said core, said secondary winding includlng two spaced equal sections arranged side by side on said core, and a conductive shleld be tween the two sections of the secondary winding, the center of the secondary wlndlng and said shield being conduct vely connected to said core, and said core bein grounded. v

In witness whereof, I have ereunto'set my hand.

transfer of hi h frequency energy from the secondary to t e primary circuit. The present invention still further reduces such transfer of high frequency energy by providing the conductive shield 19 between the two sections of the secondary winding. This mproved result is due to the fact that the shield improves the electrical symmetry between thetwo sections of the high voltage secondary winding and ground. The shield also acts as a capacitor to by-pass high frequency energy in the secondary circuit and in this wa to prevent the by-passed energy from the primary circuit to cause radio interference.

The invention has been explained by describin and illustrating a particular embo iment thereof but it will be apparent that changes may be made without departing from the spirit of the invention or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A transformer including a magnetic core, primary and seconda windings on said core, said secondary windmg including two spaced sections, and a conductive shield between the two sections of the secondary winding.

2. A transformer including a magnetic core, primary and secondary windings on said core, said secondary winding including two spaced sections, and a conductlve grounded shield between the two sections of the secondary winding.

3. A transformer including a magnetic core, primary and secondary wlndlngs on said core, said secondary winding including two spaced equal sections connected in series, the center of said secondary windin being rounded, and a conductive rounde shield between the two sections 0 the secondary winding.

4. A transformer including -a magnetic core, primary and secondary windings on said core, said secondary winding including two spaced equal sections arranged side by side on. said core, the center of said secondary winding being grounded, and a conductive grounded shield between the two sections of the secondary winding.

5. A transformer including a magnetic CHARLES w. KRONMILLER." 

